JS: Backout some of latest amount parsing changes.
JS: Backout some of latest amount parsing changes.

wilsonianb/ripple-lib,wilsonianb/ripple-lib,darkdarkdragon/ripple-lib,darkdarkdragon/ripple-lib,ripple/ripple-lib,ripple/ripple-lib,ripple/ripple-lib,darkdarkdragon/ripple-lib,ripple/ripple-lib,wilsonianb/ripple-lib